Would I have to upjet?

[37monkey]

Sorry if this has been covered before, I have looked for quite a while but couldn't see the answer, If I change the exhaust on my Pulse Adrenaline 125 to one of these http://cgi.ebay.co.uk/ws/eBayISAPI.d...T#ht_624wt_698
and fit a 16 tooth front sprocket would I have to up jet the carb? if so what to? I would prefer to stay out of the dark art of carb fettling if I can help it, I just want to be able to sit at 60mph or so comfortably.
Thanks all

[barnone]

Nice find for an exhaust. I would say that you need to increase the size of the main jet but since I don't know your bike can't suggest the size increase.

[37monkey]

I've decided not to start messing with exhaust and jets, so the bike is in the shop having a 16 tooth front spocket fitted, I'll post about the difference when the snows gone and i've had a chance to test it

[jape]

I think you have made the right decision. Expecting to cruise at 60 mph on a pretty standard 125cc machine that isn't totally rebuilt to race specs is a bit much. Yes, we could push even a Bantam 125 to those speeds with some work but you couldn't expect it to stay there and not blow up. The simplest answer for you, unless you are a rebuild enthusiast or wish to learn to be one, is move up when you can to at least a 250. A well tuned and modded 200cc Chinabike will get there and hold it but a 250cc is really the bottom-line if you are going places.

The snow still sitting in the UK? You up on the moors or something or in darkest Wales? Might have to get some studded tyres!

[choldy]

Mate I feel your pain! I'm down on the South Coast but its still too damned cold to ride. I rode to work yesterday and the bike ran like a dog to be honest, doesn't like the cold. As for the carb question, I've got an RMR200 with an aftermarket exhaust. According to the guy I got it from its running fine on standard jetting. To confirm after a 6 mile ride last night I pulled the plug, it was actually a little dry, black and sooty which I think means running rich. Before I mess with jets, I'm inexperienced like you, I'm just going to hit the workshop manual and lean out the mixture using the adjustments available on the carb. If that doesn't get me where I want to be then I'll mess with the next size up jets. I'm very interested on your experience with the 16 tooth sprocket when you get a chance to ride, I was thinking of going 16 or even 17 tooth on mine as I will only be riding on road.

[barnone]

chody,
If you are running rich like your plug reading suggests, then you might want to go with a smaller size main jet. Maybe you need to put in a new plug and take another reading to make sure that it is running too rich? Also make sure the choke is all the way off.